I don't know what Roku is but on Hulu The latest 10 episodes are available for free for 14 days(at least I think it's 14.) then they expire one by one. After they expire the episode can only be viewed by Hulu Plus members.

For example; The Premiere episode of OLTL has expired for the free users, but if you have Hulu Plus then you can still view it anytime you want.